We are applying path and segregation analysis to mental retardation in Hawaii to resolve cultural and biological determinants. Cytological bands are being assigned genetic locations from chiasma distributions, with derivation of a mapping function for man. Sources of variation in satellite association, nondisjunction, and polypoidy are under analysis. BIBLIOGRAPHIC REFERENCES: Morton, N.E. Genetic Markers in Atherosclerosis: A review. J. Med. Genet. (in press). MacLean, C.J., Morton, N.E., Elston, R.C., and Yee, S. Skewness in Commingled distributions. Biometrics (in press).